Abstract
Planktonic copepods are a key group in the marine pelagic ecosystem, linking primary production with upper trophic levels. Their abundance and population dynamics are constrained by the life history tradeoffs associated with resource availability, reproduction and predation pressure. The tradeoffs associated with the ageing process and its underlying biological mechanisms are, however, poorly known. Our study shows that ageing in copepods involves a deterioration of their vital rates and a rise in mortality associated with an increase in oxidative damage (lipid peroxidation); the activity of the cell-repair enzymatic machinery also increases with age. This increase in oxidative damage is associated with an increase in the relative content of the fatty acid 22:6(n-3), an essential component of cell membranes that increases their susceptibility to peroxidation. Moreover, we show that caloric (food) restriction in marine copepods reduces their age-specific mortality rates, and extends the lifespan of females and their reproductive period. Given the overall low production of the oceans, this can be a strategy, at least in certain copepod species, to enhance their chances to reproduce in a nutritionally dilute, temporally and spatially patchy environment.
Highlights
Several species of marine copepods in the laboratory, in the absence of extrinsic mortality, have been linked recently to tradeoffs associated with species-specific feeding and mate-finding behaviours, as well as to spawning behaviours[14]
A study by Rodríguez-Graña et al.[35] has attempted to link oxidative damage and ageing in copepods. They found an increase in the levels of carbonylated proteins with age in males of the copepod Acartia tonsa, but they found no such variation in females[35]
Along with the patterns of change in routine metabolism and somatic elemental composition associated with age, P. grani females were largely able to maintain homeostasis and to sustain rather high feeding rates and reproductive activity until nearly the end of their lifespan
Summary
Several species of marine copepods in the laboratory, in the absence of extrinsic mortality, have been linked recently to tradeoffs associated with species-specific feeding and mate-finding behaviours, as well as to spawning behaviours[14]. They found an increase in the levels of carbonylated proteins (a biomarker of oxidative damage to proteins) with age in males of the copepod Acartia tonsa, but they found no such variation in females[35] Despite the latter result, current knowledge of the biology of ageing supports the view that a certain level of reactive oxygen species (ROS) is always present and is essential to maintaining homeostasis in animals. Current knowledge of the biology of ageing supports the view that a certain level of reactive oxygen species (ROS) is always present and is essential to maintaining homeostasis in animals It appears that shifts in the delicate balance among ROS generation, antioxidant defences and cell-repair systems might be the links among oxidative damage, ageing and lifespan[18,36,37]. This likely is a life-history strategy to ensure reproductive investment in the ocean, a nutritionally dilute, temporally and spatially patchy environment[39,40]
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